PROJECT SUMMARY AND RELEVANCE We recently described the ?Continued transmission of Zika virus in humans in West Africa 1992-2016?.1 While the long-term endemicity of Zika virus (ZIKV) and related flaviviruses in Africa had long been suspected, the 2015-16 ZIKV epidemic in the Americas and the associated microcephaly raised questions as to why we had not recognized these distinct neurologic and congenital abnormalities in Africa. Genetic analysis has distinguished African and Asian ZIKV lineages that have been postulated to be responsible for the dramatic transmissibility and unique disease association recognized in the 2015-6 epidemic of the Americas. However, increased recognition of the distinction between the ZIKV lineages has resulted in studies that demonstrate similar transmission dynamics, neurotropism in cell culture systems and neurologic pathology or lesions in cerebral organoids and murine models.3-6 Therefore, it is critical that the epidemiology and clinical consequences of ZIKV in Africa be determined. We propose studies that will provide new data on the prevalence of ZIKV, Dengue virus (DENV) and Chikungunya virus (CHIKV) in pregnant women in north-central Nigeria. We will determine if infants born to women in West Africa infected with ZIKV may be at high risk for microcephaly and/or congenital ZIKV syndrome (CZS). Our long-term collaborators in Jos, Nigeria will recruit pregnant women attending two active antenatal clinics (ANC). In response to reviewer suggestions, this revised application doubles the number of pregnant women visits in order to increase the potential number of ZIKV infected pregnant women identified. Women will be screened with a point of care ZIKV, DENV, CHIKV assay and further confirmed through nucleic acid detection. We now estimate the identification of 320 ZIKV infected pregnant women for prospective evaluation through delivery and evaluation of infants until 6 months of age for microcephaly or CZS development. Through full length sequence analysis of ZIKV from pregnant women and affected infants, we will assess the ZIKV viral lineage using both unbiased metagenomic and targeted ZIKV sequencing approaches and compare to the lineages from the 2015-16 outbreak in the Americas. Relevance Environmental suitability modeling of ZIKV predicts that in Africa, Nigeria is the country with the highest risk for ZIKV transmission.26 The impact of African ZIKV on pregnancy outcomes is unknown and research to address this question is paramount to global public health and outbreak preparedness.